When structuring a network system such as for OA (Office Automation) or FA (Factory Automation) wherein a facility such as a building or a plant is controlled by a computer, typically the system is structured by defining in advance locations wherein various types of devices such as air conditioners, elevators, valves, sensors, and the like are disposed, and then, after generating and editing various data for setting up these devices using an engineering device, downloading, to the individual devices, the data that has been set up.
In such engineering devices, when downloading a new control program or setup data to a controller for controlling an equipment instrument, the applicable controller is first switched into an off-line state, which temporarily stops the various control programs that are being executed, after which the new control program and/or setup data is downloaded, and the control program is restarted after the download has been completed.
Conventionally, in order to avoid the control of the equipment instrument from being stopped through stopping the control program when downloading in this way, there have been proposals for technologies for downloading the new control program or setup data in an on-line state with the control program is still running, rather than going into an off-line state wherein the control program that is being executed by the controller is stopped, and then, upon completion of the download, switching from the original control program to the new control program. See, for example, Japanese Unexamined Patent Application Publication No. 2001-333128.
However, this type of conventional technology, merely switches to a new control program or setup data from the original control program in the controller, and operations are continued for the other control programs. Because of this, this may cause, within the controller, a mismatch between the default process data used by the new control program that is restarted and the processing data currently used for those the existing control programs that continue to operate that are linked control programs that are operating in coordination with the new control program, and, and thus there is a problem in that this may cause instability in the state of operation between the linked control programs and the new control program.
The present invention was created in order to solve such an issue, and an aspect thereof is to provide a download processing technology able to preserve a stabilized operating state even when replacing, with new control programs, a portion of the control programs that are running in a controller.